A set of standards (EN 50221) of using conditional access (CA) implemented in a module via a common interface (CI) has been issued and used in order to deal with conditional access of different paths at the time of receiving a television broadcast.
FIG. 13 illustrates a configuration example of a reception system 300 in digital broadcasting based on the set of standards (EN 50221). The reception system 300 is constituted of a host device 310 and a CAM module 302.
The host device 310 is a television receiver set (TV set), a set-top box, or the like. The host device 310 has a microprocessor 311, a tuner 312, and a demodulator 313. In addition, the host device 310 has a demultiplexer 314 and an MPEG decoder 315. Operations of each of the units of the host device 310 are controlled by the microprocessor 311.
The CAM module 320 is an attachment device for performing a descrambling process which fits into a DVB-CI common interface connector of the host device 310. The CAM module 320 is used by inserting a smart card 330 such as a magnetic card or an IC card in which subscriber information, subscription contract period information, and the like are recorded into the CAM module. The CAM module 320 has a microprocessor 321 and a descrambler 322. Operations of each of the units of the CAM module 320 are controlled by the microprocessor 321.
The tuner 312 of the host device 310 receives RF modulated signals of transport streams TS transmitted from a broadcasting station. In addition, the RF modulated signals are down-converted in the tuner 312 so as to have an intermediate frequency (IF) and then output so as to be input to the demodulator 313. The demodulator 313 demodulates the IF modulated signals that have been down-converted so as to have the intermediate frequency, and thereby a transport stream TS of a baseband is obtained. The transport stream TS is transmitted to the CAM module 320 via the DVB-CI common interface.
The CAM module 320 receives the transport stream TS transmitted from the host device 310 via the DVB-CI common interface, and then the descrambler 322 performs a descrambling process on the transport stream. Then, the CAM module 320 transmits the descrambled transport stream TS to the host device 310 via the DVB-CI common interface.
The host device 310 receives the transport stream TS transmitted from the CAM module 320 via the DVB-CI common interface. The demultiplexer 314 extracts video and audio PID data packets of a selected (tuned) service channel from the received transport stream TS. The MPEG decoder 315 decodes an elementary stream constituted of the PID data packets extracted by the demultiplexer 314, thereby obtaining video data and audio data.
FIG. 14 illustrates a configuration example of a PVR (Personal Video Recorder) 400 with which taping and viewing can be performed at the same time. The PVR 400 has a controller 401, tuners 402-1 and 402-2, demultiplexers 403-1 and 403-2, a storage 404, a changeover switch 405, and an MPEG decoder 406. Operations of each of the units of the PVR 400 are controlled by the controller 401. Here, the tuners 402-1 and 402-2 correspond respectively to the tuner 312 and the demodulator 313 of the host device 310 of FIG. 13.
The tuners 402-1 and 402-2 respectively receive RF modulated signals of transport streams TS1 and TS2 transmitted from a broadcasting station. In addition, the tuners 402-1 and 402-2 down-convert the RF modulated signals so as to have an intermediate frequency (IF), and then demodulate the IF modulated signals, thereby obtaining the transport streams TS1 and TS2 of a baseband.
The demultiplexers 403-1 and 403-2 respectively extract video and audio PID data packets of a selected (tuned) service channel from the transport streams TS1 and TR2. The video and audio PID data packets extracted by the demultiplexer 403-1 are input to the side of the changeover switch 405. On the other hand, the video and audio PID data packets extracted by the demultiplexer 403-2 are input to the storage 404. The video and audio PID data packets of the predetermined service channel reproduced from the storage 404 are input to the b side of the changeover switch 405.
During taping and viewing in which taping and viewing are performed at the same time, the video and audio PID data packets extracted by the demultiplexer 403-2 are recorded in the storage 404. In addition, in this case, the changeover switch 405 is connected to the side, and the video and audio PID data packets extracted by the demultiplexer 403-1 are selectively extracted. Then, the MPEG decoder 406 decodes an elementary stream constituted of the PID data packets, thereby obtaining video data and audio data.
In addition, during reproduction, the PID data packets of the predetermined service channel are reproduced from the storage 404. In addition, in this case, the changeover switch 405 is connected to the b side, and the video and audio PID data packets reproduced from the storage 404 are selectively extracted. Then, the MPEG decoder 406 decodes an elementary stream constituted of the PID data packets, thereby obtaining video data and audio data.
When the technology of the set of the standards (EN 50221) described above is applied to the PVR 400 by which taping and viewing can be performed at the same time, using two CAM modules is considered. However, since using two CAM modules is possible but uneconomic, it is desirable to enable one CAM module to descramble two transport streams TS1 and TS2 at the same time as in the principle illustrated in FIG. 15.
However, according to the set of standards (EN 50221), since there is only one interface each of transport streams that can be used on a common interface (CI) for input and output, it is necessary to perform time-division multiplexing on TS packets of two transport streams and to make one stream. For example, Patent Literature 1 discloses that time-division multiplexing is performed on TS packets of two transport streams so as to make one stream, and thereby the stream is transmitted between a host device and a CAM module connected by a common interface (CI).